The present invention relates to an optical fiber laser conducting device used for a therapy using laser beams (rays) guided by optical fibers, particularly used for a laser dynamic therapy for early cancer called a photodynamic therapy (PDT).
A therapeutic method for cancer utilizing the light and heat effect of laser, particularly the laser dynamic therapy for early cancer known as the photodynamic therapy is performed by permitting laser beams generated by a laser generator incident on a guiding portion of optical fibers, that is, on a core portion making use of an optical system, and guiding and applying the laser beams to the affected parts within the body such as lung, gullet, stomach, uterus, bladder and the like making use of bending properties of the optical fibers.
In this case, it is often that the introduction of the optical fibers into the affected parts is carried out in such a manner that the optical fibers are inserted through a forceps of an endoscope, and a laser irradiation to the affected parts is carried out while being observed by a doctor.
It is often that the laser beams generally used comprise pulse wave in order to enhance the efficiency. In this case, an irradiation dose of laser beams is expressed by the product of a laser output per pulse (joule/pulse), frequency of pulses (pulse/second) and time (second or minute). The irradiation dose of laser beams is an important factor in therapy.
In many cases, an optical system called a "tip" adjusted to the shape of the affected part is mounted at the extreme end of the optical fibers from which laser beams go out in order to effectively apply the laser beams to the affected part.
One form of the above tip is of a forward direct type, in which case there gives rise to one problem in an evenness of a pattern of laser strength over the whole area from a center portion to a peripheral portion of a laser spot irradiated and projected to the forward affected part, as is apparent from the above explanation of the irradiation dose of the laser beams.
Even in prior arts, for example, a laser device using a spherical lens at the tip as disclosed in Japanese Utility Model Application Laid-Open No. 6(1994)-8910 publication, and a laser device using a cylindrical GRIN lens at the tip made by Nippon Sheet Glass Co., Ltd. known as a "SELFOC Lens", the necessity of the evenness of the pattern of the laser outgoing strength of the forward direct type has been aware of.
These prior arts have both merits and demerits such that they are expensive, that the evenness of the pattern of irradiated laser pattern is unsatisfactory, that when a focal point is concentrated on a specific portion within the lens due to the reflection within the lens of an impulse wave of a pulse laser, the lens has a possibility of being broken, and that contaminations of the tip generated by the scattering or evaporation of body fluids caused by the laser wave during the therapy is difficult to clean and remove.